1. Field of the Invention
The present invention relates to heat exchange systems used for open heart surgery. More particularly, the present invention relates to systems used for the cooling, heating and recirculating of fluids associated with arterial/venous and cardioplegia fluid lines in cardiovascular surgery.
2. Description of Invention
Typically, a circulatory support and cardioplegia administration system includes (among other things) a venous catheter for draining blood from the patient""s venous system, a venous line for transferring blood drained with the venous catheter to a venous reservoir, a heat exchanger and an oxygenator connected via a transfer line to the outlet of the venous reservoir, and an arterial line connected to the outlet of the oxygenator to supply the oxygenated blood to a cannula, which returns the blood to the patient""s heart. Such systems have included other components or subsystems as well. One such subsystem relates to blood recovery from the surgical site (e.g., the pericardial sac) and that system would include a number of blood suction devices (intracardiac suckers) that supply blood to the cardiotomy reservoir that collects, defoarns and filters the recovered blood before supplying it to the venous reservoir of the main system.
Another subsystem is the cardioplegia administration system. Cardioplegia is a commonly used technique for protecting the heart during heart surgery. Typically, cooled cardioplegia solution (e.g., a potassium solution, cooled blood or a blood/potassium solution) is administered to the patient""s heart in either the antegrade or retrograde direction through either the patient""s aorta or coronary sinus, respectively. xe2x80x9cAntegradexe2x80x9d refers to the direction of normal blood flow, and xe2x80x9cretrogradexe2x80x9d refers to the direction opposite of normal blood flow.
The cardioplegia solution stops the heart and reduces its temperature to minimize damage to the heart during surgery. Such cardioplegia solutions are typically introduced into the heart in an intermittent fashion. For example, a bolus of cooled cardioplegia solution may be delivered to the heart to initially arrest the heart, and then the subsequent doses of the cardioplegia solution may be administered approximately every 15-20 minutes.
Cardioplegia subsystems have included a heat exchanger connected to a source of cardioplegia solution and/or blood, a bubble trap to collect air emboli to prevent supplying such emboli to the patient, a temperature monitor for measuring and displaying the temperature of the cardioplegia solution downstream of the heat exchanger, a cardioplegia supply line connected to the outlet of the bubble trap/temperature monitor, and a catheter connected to the downstream end of the cardioplegia supply line for supplying the cardioplegia solution to the heart.
In the past, separate systems have been used for the heating and cooling of the arterial supply line and the heating and cooling of the cardioplegia supply line. Since the arterial supply line and the cardioplegia supply line are separate and independent circuits, independent systems have often been used for the heating and cooling of the fluids within such supply lines. Unfortunately, the use of separate heating and cooling systems occupies a great deal of space within the operating room. The footprint within the operating room is extremely limited. As a result, additional heating and cooling systems can occupy an excessive amount of space. Each of the separate heating and cooling systems requires its own cooling or ice bath. Additionally, each of these heating and cooling systems will require separate heating facilities.
Very importantly, each of the heating and cooling systems will utilize separate 1500 watt heaters. Each of these 1500 watt heaters will draw approximately sixteen amps worth of power. When each of the heaters is on simultaneously, the power draw will be approximately thirty amps. This will be in excess of the twenty amp power supply which would be available for such heaters. As a result, in the open heart surgery operating environment, when both of the heaters for the separate systems are activated, circuit breakers will trip and cause the systems to shut down. As such, it is very important to avoid the excessive draw of amperage from the power supply. Furthermore, when both of the systems are activated at the same time, a spike of current can occur which can damage other equipment within the operating room environment. So as to maintain the integrity and reliability of the other equipment in the operating room environment, it is very important to avoid power surges or current spikes.
It is an object of the present invention to provide a fluid heating system which avoids unnecessary power surges, spikes, and current draw.
It is another object of the present invention to provide a heating system for use in open heart surgery which does not require separate systems for the heating and cooling of the separate fluid lines.
It is a further object of the present invention to provide a heating system for use in open heart surgery which can be operated from a single power outlet.
It is a further object of the present invention to provide a heating system for use in open heart surgery which minimizes space usage in the operating room environment.
It is still a further object of the present invention to provide a heating system for use in open heart surgery which prevents the simultaneous operation of the separate heaters.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.
The present invention is a blood heating system for use in open heart surgery comprising a first fluid circuit, a second fluid circuit defining a fluid flow path independent of the first fluid circuit, a first heater in heat exchange relationship with the first fluid circuit, a second heater in heat exchange relationship with the second fluid circuit, a power supply connected to the first and second heaters so as to supply a desired electrical power to the first and second heaters, and a controller electrically connected to the power supply and to the first and second heaters such that the first and second heaters cannot be activated simultaneously.
In the system of the present invention, each of the first and second heaters are of a type that draw between 15 and 20 amps of electrical energy from the power supply. The controller is a relay which is interconnected between the heaters and the power supply. The relay serves to deactivate one of the heaters when the other of the heaters is activated. A timer can be connected to the relay so as to activate and deactivate each of the heaters after a desired period of time such that each of the heaters will heat alternately. The timer will activate the first heater when the first heater is deactivated and activate the second heater after the first heater is deactivated. The timer will serve to activate and deactivate the respective heaters after a desired period of time (e.g. four seconds).
In the present invention, the power supply is a single 110 volt source of electrical energy providing twenty amps of power. The relay serves to energize one of the heaters as the other of the heaters is de-energized. The relay includes a first solid state relay interposed between the power supply in the first heater. The first solid state relay can be switched by the controller so as to pass AC power from the power supply to the first heater. A second solid state relay is interposed between the power supply and the second heater. The second solid state relay is switched by the controller so as to pass AC power from the power supply to the second heater. The power supply is from a single electrical outlet.
The controller of the present invention can further include a first sensor which is interactive with the first fluid circuit so as to sense a temperature of a fluid within the first fluid circuit. The first sensor is electrically connected to the first solid state relay so as to activate the first heater when the temperature of the fluid in the first fluid circuit is below a desired level. A second sensor is interactive with the second fluid circuit so as to sense the temperature of a fluid in the second fluid circuit. The second sensor is electrically connected to the second solid state relay so as to activate the second heater when the temperature of the fluid within the second fluid circuit is below a desired level. A DC power supply can be connected to the first and second heaters so as to supply electrical energy to the first and second solid state relays so as to switch the respective relays. The first sensor can deactivate the first heater when the temperature of the fluid is above a desired level. The second sensor can deactivate the second heater when the temperature of the fluid is above a desired level.
The present invention is also a method of heating fluid circuits used in open heart surgery. This method includes the steps of: (1) connecting a first heater in heat exchange relationship to the first fluid circuit; (2) connecting a second heater in heat exchange relationship with the second fluid circuit; (3) supplying electrical energy to the first and second heaters from a single power supply; and (4) deactivating one of the first and second heaters when the other of the first and second heaters is activated such that the heaters cannot be activated simultaneously. This step of deactivating includes switching one of the heaters to an active state as the other of the heaters is deactivated. Power is supplied to the first and second heaters such that the first and second heaters never draw cumulatively more than 20 amps of power from the single power supply. A first relay is connected to the first heater. A second relay is connected to the second heater. The first relay activates the first heater when the second relay deactivates the second heater. The step of switching can include the use of a timer which alternates the first and second heaters between the active state and the deactive state for a desired period of time.